5.2.7

Respiration Experiments

Test yourself

Investigating Respiration in Single-Celled Organisms (Yeast)

Yeast respires aerobically and anaerobically. During aerobic respiration, the transport of electrons is linked to the synthesis of ATP. This experiment will measure the rate at which this takes place.

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Methylene blue

  • In this investigation, the electrons that are transported down the ETC will be accepted by a substance called methylene blue.
  • Methylene blue is a redox indicator.
    • This indicator is blue in the oxidised state and colourless in its reduced state.
  • As the rate of respiration increases, methylene blue will turn colourless more quickly.
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1) Mix yeast with glucose

  • Use the beaker to set up a water bath at 35°C.
  • Label five test tubes 1 to 5.
  • Shake the yeast and glucose mixture.
  • Add 2 cm3 of the yeast and glucose mixture to all five tubes.
  • Place all five tubes in the water bath and leave them until the contents reach 35°C. Make sure the water bath stays at 35°C.
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2) Add methylene blue

  • Add 2 cm3 methylene blue to test tube 1.
  • Immediately shake this tube for 10 seconds and replace the tube in the water bath. Note the time and do not shake this tube again.
  • Record how long it takes for the blue colour to disappear in the tube.
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3) Repeat the experiment

  • Repeat steps 1 and 2 for the other four tubes.
  • Repeat the whole experiment in water baths at different temperatures:
    • 15°C.
    • 25°C.
    • 45°C.
    • 55°C.

Jump to other topics

1Biological Molecules

2Cells

3Substance Exchange

4Genetic Information & Variation

5Energy Transfers (A2 only)

6Responding to Change (A2 only)

7Genetics & Ecosystems (A2 only)

8The Control of Gene Expression (A2 only)

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